Prior art knock-out constructions commonly leave burrs or jagged edges projecting into a knock-out opening which remains when the knock-out is removed. These burrs can damage electrical cables passed through the openings and also can scratch or cut the fingers of users of these devices.
In addition, when used in a housing for electrical equipment, it is desirable that knock-out designs provide electromagnetic interference shielding in the event the knock-out is not used. Prior art constructions typically do not address the need for electromagnetic interference shielding.
Also, it is desirable that a knock-out design which is easy to manufacture, which has sufficient integrity to resist removal due to inadvertent impact, and which is easy to remove when desired without requiring special tools.
Therefore, a need exists for an improved knock-out construction which addresses these and other problems of the prior art.